An Introduction to Atrial Fibrillation, Life Expectancy and Medico-Legal Applications
by Mr Paul D Ridley, Consultant Cardiothoracic Surgeon
Atrial fibrillation is a heart condition that causes an irregular, often rapid heart beat that commonly causes poor blood flow. It’s the most commonly occurring sustained cardiac arrhythmia in the UK population occurring in more than a million people.
In this article I will explain:
- The difference between a normal heart rate and atrial fibrillation
- The relationship between atrial fibrillation and life expectancy
- How to measure the heart rate
- Who’s more at risk to atrial fibrillation
- How atrial fibrillation is treated
- 3 case studies where I ruled on atrial fibrillation
The Difference Between A Normal Heart Rate And Atrial Fibrillation
The normal heart rhythm is a regular sinus rhythm which is characterised by contraction of the two atrial chambers followed soon after by contraction of the two ventricular chambers of the heart for each beat of the heart. This is indicated by a regular pulse within the normal heart rate range which at rest is between 60 and 100 beats per minute.
In atrial fibrillation, the regular organised atrial contraction is replaced by chaotic electrical activity within the atria so that there are multiple uncoordinated small electrical circuits within the atrial muscle and the muscle fibrillates looking like a bag of worms. The atrial contractile function and its contribution to cardiac output is lost and the atria function as a conduit for blood transit rather than a pump.
Typically, atrial fibrillation presents as an intermittent phenomenon being paroxysmal. It increases in frequency and length of episode. It eventually becomes continuous (persistent) as the atrial chambers of the heart remodel electrically and morphologically with a tendency for the atrial walls to thicken and the cavity size of the atria to enlarge. Atrial fibrillation begets atrial fibrillation.
Atrial fibrillation is usually associated with a tachycardia. The patient experiences palpitations associated with the rapid irregular heart rate. The earlier stages of intermittent (paroxysmal) atrial fibrillation may be more troublesome to a patient than the later stages with continuous (persistent) atrial fibrillation. Rather like a flashing light catches the eye more than a constant light, the patient may find intermittent symptoms more noticeable and therefore more troublesome than continuous arrhythmia.
The Relationship Between Atrial Fibrillation And Life Expectancy
Atrial fibrillation is associated with a reduction in life expectancy. It’s independently associated with a 2 fold increase in mortality for women and a 1.5 X increase in men. Overall, because of associated co-morbidities, there is a 3.5X increase in mortality.
There is a loss of atrial kick and a reduced cardiac output. There is a greater tendency for stasis of blood and therefore for thrombosis within the atria. This is more so in the left atrium than in the right atrium. The anatomy of the left atrial appendage shows a narrower neck and the right atrial appendage is washed by the direction of venous return from the inferior vena cava. So we see left-sided embolic phenomena such as strokes and embolic limb ischaemia rather than right-sided pulmonary emboli resulting from atrial fibrillation. Atrial fibrillation is related to a 5X incidence of embolic stroke being associated with 20-30% of all ischaemic strokes.
How To Measure The Heart Rate
The heart rhythm may be investigated with an electrocardiogram (ECG) trace of the heart by which the electrical activity of the heart is traced on a strip or sheet of paper. Usually this makes a trace of 12 leads looking at the electrical activity from 12 different angles from the chest. This is a quick and non-invasive examination in which electrodes are placed on the chest, wrist and ankles and a trace is collected over about 30 seconds.
There are devices that collect traces over 24 hours, 48 hours or longer which attach to the patient for longer periods. The patient may be attached to an ECG monitor whilst an in-patient to obtain a continuous single lead display to monitor heart rhythm.
Who’s More At Risk To Atrial Fibrillation?
The risk of atrial fibrillation increases with age. It’s less than 1% in those under 50 years of age and rises to an incidence greater than 3% in those over 60 years of age. The incidence is greater than 10% in those over 80 years of age. It is more common in men than women.
It’s associated with a number of co-morbidities, being more common in smokers, diabetics and those with increased body mass index. It’s also associated with hypertension, a history of myocardial infarction, a history of heart failure, high alcohol intake, chronic kidney disease and obstructive sleep apnoea. It is associated with a sedentary lifestyle but is also associated with prolonged long-distance running over many years.
How Atrial Fibrillation Is Treated
Medications are used to treat atrial fibrillation. Antiarrhythmic medications may aim to slow the heart rate in atrial fibrillation (rate control) or convert the atrial fibrillation to normal sinus rhythm (rhythm control). Antiarrhythmics may have side effects. Typically anticoagulation is also used to treat atrial fibrillation to decrease the risk of thrombosis and emboli. Anticoagulation is associated with an increased risk of bleeding phenomena.
Atrial fibrillation may be treated by more invasive measures. Via venous access, cardiologists may introduce catheters into the heart and radiofrequency ablate areas of the atria aiming to block the abnormal conduction and restore sinus rhythm. The cardiologist may introduce a device within the left atrium to occlude the left atrial appendage. The cardiothoracic surgeon may also perform radiofrequency ablation lesions on the atria of the beating heart through limited access thoracic incisions or on the arrested heart under cardiopulmonary bypass (open heart surgery). This is invasive and is typically performed concomitantly at the time of open heart surgery on other parts of the heart for example mitral valve surgery. The surgeon may close the left atrial appendage with purpose designed clip.
3 Case Studies Where I Ruled On Atrial Fibrillation
Case Study 1 – Clinical Negligence
A 67-year-old man underwent a three-vessel coronary artery bypass graft operation and made an initial routine recovery. As per routine protocol, he was treated with a low-dose beta blocker and aspirin and low-dose subcutaneous heparin in the early postoperative period. On the third postoperative day, he experienced atrial fibrillation. An antiarrhythmic medication managed this, Amiodarone and normal sinus rhythm was restored by the fifth postoperative day.
He was discharged home on medications including Amiodarone and followed up in the outpatient clinic. He had no further symptoms of palpitation. He had routine examinations and ECG investigations on several occasions and was found to have a regular pulse and ECG trace with normal sinus rhythm. Three months postoperatively he had no history of palpitation and ECG confirmed normal sinus rhythm and the Amiodarone was discontinued. He remained on beta-blockade and aspirin medication. He remained in sinus rhythm on subsequent follow-ups.
The client complained that there was a failure in medical care as the open heart surgery had caused atrial fibrillation. We agreed that the open heart surgery had caused the atrial fibrillation. But we noted that atrial fibrillation was an accepted complication of open heart surgery, which occurs in more than 20% of cases. Typically such postoperative atrial fibrillation is prone to occur in the first week after open heart surgery and then becomes less likely and reverts to and remains in preoperative sinus rhythm.
Case Verdict – The Client Has No Claim
Full anticoagulation is not usually required. He was managed in an appropriate and standard manner so we saw no failure of duty of care in this case.
Case Study 2 – Personal Injury
A 70-year-old woman was driving a motor car involved in a head-on road traffic accident. She was wearing a seat belt and had a headrest. Airbags were deployed. The car was a write-off. Emergency services employed cutting gear to free her from the vehicle. She was taken by ambulance to the hospital and a CT scan showed an undisplaced fractured sternum. The transthoracic echocardiogram showed no abnormality. There was a mild elevation in cardiac enzymes.
She was monitored in the accident and emergency department and it was noted that she had episodes of fast atrial fibrillation on the ECG monitor. She was admitted to the hospital and observed and treated with analgesics. In the hospital 3 further episodes of atrial fibrillation were noted. A cardiology opinion was obtained and she was treated with a low-dose beta blocker oral medication. She was managed conservatively and after 6 days was discharged home on oral analgesic and beta-blocker medication.
On discharge home, she made a good recovery from the fractured sternum and the pain settled. However, she continued to experience palpitations with increasing frequency. Prior to the road traffic accident, she had never experienced palpitations and had never had a diagnosis of atrial fibrillation. She had non-insulin-dependent diabetes and an increased body mass index. Cardiologists introduced further antiarrhythmic and anticoagulant medication. Twelve months after the road traffic accident she was clinically stable and active in rate-controlled atrial fibrillation and antiarrhythmic and anticoagulant medications.
The client claimed that the atrial fibrillation had been caused by the road traffic accident and she had suffered because of this. The defendant suggested that (1) She may have had occult atrial fibrillation prior to the road traffic accident. (2) She would have developed atrial fibrillation even had she not suffered the road traffic accident. (3) She had not suffered harm although she was in atrial fibrillation as it was a well-tolerated common arrhythmia and she was doing well with medical management.
We acknowledged that it was possible that she may have had undiagnosed atrial fibrillation prior to the road traffic accident. However, there was no past medical history of this. Also, we note that prior to the road traffic accident, there were no symptoms of palpitation which she experienced with the documented episodes of paroxysmal atrial fibrillation.
We were impressed by the time course of the onset of the atrial fibrillation occurring immediately after the chest trauma. Sternal fracture in isolation without cardiac injury rarely results in atrial fibrillation but it is described and is more common in the elderly. Chest trauma may initiate the onset of atrial fibrillation in those more prone to it. We found that on the balance of probability, the chest trauma did cause atrial fibrillation. We noted that the client was clinically well at the time of examination but that the atrial fibrillation could potentially cause complications as could the medications used to treat it.
Case Verdict – The Client Has A Claim
We, therefore, found that not only had the trauma caused atrial fibrillation in this case but that the atrial fibrillation on the balance of probability could lead to harm.
Case Study 3 – Clinical Negligence
It is routine to anticoagulate patients following mechanical heart valve replacement and Warfarin (which has been used as a rat poison) is usually employed. The level of warfarinisation is important as if is too much bleeding complications may occur (as in the rats) and if too low the valve may get thrombus and embolic phenomena may occur. The level of warfarinisation is monitored by a bleeding time blood test called International Normalised Ratio (INR). In the non-treated person INR=1.0 and as the warfarin dose is increased it becomes elevated. At twice the baseline (INR=2.0).
A 55-year-old woman underwent open heart surgery with a mechanical aortic valve designed to function with less postoperative anticoagulation. This valve is advertised as having a decreased risk of thromboembolic complication and therefore less anticoagulation may be used in the postoperative period. In the six-month period following the heart surgery, the client described intermittent palpitation.
Her ECG on occasion showed sinus rhythm and on other occasions showed atrial fibrillation in this 6-month postoperative period. As per the advised protocol for this type of mechanical heart valve, the Warfarinisation was decreased 3 months after the open heart operation. Nine months after the heart operation the client suffered a left-sided embolic injury. Her warfarinisation was then increased.
The client complained that the Warfarin medication had been decreased too low for use in a mechanical heart valve and that this represented a failure of duty of care. This failure of duty of care then caused an embolic injury.
We found that the plan to reduce the level of anticoagulation was reasonable as there was trial evidence and expert guidelines supporting this approach for this specific type of mechanical valve type. Many cardiac surgeons would use the lower INR level to manage this valve type postoperatively. However, the protocol was predicated upon the postoperative normal sinus rhythm.
It was not possible to ascertain how much atrial fibrillation had occurred postoperatively or whether atrial fibrillation had been present in the months before the embolic event as no attempt had been made to document the postoperative heart rhythm over a prolonged period. We found evidence of postoperative atrial fibrillation. The evidence would have been consistent with paroxysmal atrial fibrillation occurring for several months after open heart surgery.
On balance, we found this lack of curiosity about the heart rhythm to be a failure in duty of care in this case. There was evidence on the balance of probability that there had been significant postoperative atrial fibrillation and on the balance of probability, this had contributed to the embolic event.
Case Verdict – The Client Has A Claim
We found that reducing the warfarinisation before establishing that the client was in normal sinus rhythm represented a failure in duty of care.
Want to Discuss Your Clinical Negligence Claim with Mr Ridley?
Mr Paul Ridley is a Consultant Cardiothoracic Surgeon who retired from the Royal Stoke University Hospital in October 2022 after 25 years in the position. He is an expert in adult heart surgery, mitral valve repair, surgery for atrial fibrillation, coronary artery bypass and thoracic trauma.
Mr Ridley has been undertaking medico-legal reporting since 2000 undertaking 10-20 reports a year dealing with predominately complex serious injury and medical negligence. His Claimant – Defendant – Joint ratio is approximately 80:15:5 and he has attended trial on 2 occasions.
To contact Mr Ridley for any enquires email paulridley@inneg.co.uk
